2022 Fiscal Year Final Research Report

Theoretical study on binary black hole formation

Planned Research

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Project Area	Gravitational wave physics and astronomy: Genesis
Project/Area Number	17H06360
Research Category	Grant-in-Aid for Scientific Research on Innovative Areas (Research in a proposed research area)
Allocation Type	Single-year Grants
Review Section	Science and Engineering
Research Institution	Tohoku University
Principal Investigator	Omukai Kazuyuki 東北大学, 理学研究科, 教授 (70390622)
Co-Investigator(Kenkyū-buntansha)	須佐元甲南大学, 理工学部, 教授 (00323262) 町田正博九州大学, 理学研究院, 准教授 (10402786) 谷川衝東京大学, 大学院総合文化研究科, 助教 (20550742) 細川隆史京都大学, 理学研究科, 准教授 (30413967) 藤井通子東京大学, 大学院理学系研究科(理学部), 准教授 (90722330)
Project Period (FY)	2017-06-30 – 2022-03-31
Keywords	ブラックホール / 星形成 / 連星形成
Outline of Final Research Achievements	The origin of black hole (BH) binaries, which are gravitational wave sources, was investigated through theoretical research. The main results obtained are as follows: 1)Concerning the formation of isolated massive binary systems, we studied the properties of massive binaries that could form in the low-metallicity environment of the early universe. We found that the first stars can form as massive binary systems with masses ranging from several tens of solar masses.　2) The evolution of low-metallicity binary systems was examined using an analytical model. We demonstrated that there is no contradiction even if all the BH mergers observed through gravitational wave detection originate from isolated binary systems.　3) The formation rate of binary black holes due to dynamic interactions between stars was estimated through gravitational N-body simulations of cluster evolution. We found that even in open clusters, binary black holes can form through the dynamic interactions between stars.
Free Research Field	宇宙物理学
Academic Significance and Societal Importance of the Research Achievements	理論研究により、様々な形成シナリオの下でブラックホール連星の性質を予言することで、今後さらに質量ともに増える観測データとの比較を通じて、BH連星形成過程を解明するための理論的基盤を整備することが出来た。またブラックホール連星の起源という問題は一般の方々にも関心が深いテーマであり、社会的なインパクトも大きいといえるだろう。